1. Field of the Invention
The present invention relates to electrohydraulic rotary brakes comprising notably an inner core, at least one energizing winding, a cylindrical amagnetic insert, an annular part outside the core and the insert and including a cylindrical bore excentric with respect to the cylindrical peripheral surface of the insert, recesses provided with magnetisable sliding vanes and a brake fluid.
2. Description of the Prior Art
In this type of brake constituted in a way by a volumetric vane pump, entirely or partly filled with a fluid preferably incompressable, the vanes, fast to the rotary member, are actuatable radially whilst being guided in their respective recesses. Thus, at the moment when braking must take place, a variation in current in the energizing winding acts successively during one revolution on all the vanes to bring them to partition the cylindrical bore of the annular part excentric with respect to the insert. In a way, the vanes define peripheral chambers of different volumes. The forced passage of fluid, causing an intense throttling of fluid between the vanes and the fixed members of the pump, is the source of the braking torque which the device must develop.
According to a known construction, the inner core, immobile in rotation and axially, is a magnetic material and includes a circular peripheral cavity in which the toric energizing winding is housed, the whole being enveloped by the cylindrical amagnetic insert and constituting the fixed or stator member. The outer annular part constitutes the rotary member, or rotor, fast to the body to be braked, and it is this which includes the recesses provided with magnetisable sliding vanes. When no braking action is desired, no current is supplied to the energizing winding, and the vanes are held in the annular rotor, remote from the stator, under the action of centrifugal force. When braking is desired, the current is established in the energizing winding, and the vanes are thus attracted to the stator which causes the partitioning of the cylindrical bore mentioned above and consequently braking, provided that the intensity of the electrical current is sufficient to overcome the different forces which are opposed to the movement of the vanes in this direction. The larger or smaller amount of throttling is determined by the force of application of the vanes to the stator, depending on the energizing current passing in the electromagnetic field winding.
However, cases exist where difficulties of a technological type occur when it is desired to form the inner part of the brake in the shape of an amagnetic cylindrical rotor arranged annularly and fast to the mass to be braked. There are also cases where it is desirable for the braking to be effected by suppression of the energizing current and not by the establishment of the current (for safety reasons, for example).
It is an object of the invention to overcome one or more of these difficulties. Other objects of the invention will appear from the description which follows.